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Ornithodira: Avoid this taxon!

One core and basis of the Pterosaur Heresies blog is to demonstrate that, how and why pterosaurs have nothing in common with dinosaurs or their precursors, despite reams of traditional literature promoting that relationship. For example:

“Pterosaurs and dinosaurs have been grouped together for along time, and today, the prevalent view among vertebrate paleontologists is still that they do indeed form a natural group of animals.”— Nick Fraser (2006) in “Dawn of the Dinosaurs.”

If this false paradigm continuesanother two years that will complete a full three decades of belief in the official, “Ornithodira,” the clade THEY say includes both pterosaurs and dinosaurs. I say ‘belief’ because there’s absolutely no evidence for this relationship — as traditional paleontologists themselves have noted (see below).

“Pterosaurs appear suddenly in the fossil record and in full possession of all their highly derived characters…”— David Hone and Michael Benton (2007, 2008).

“As Figure 4.3 illustrates, paleontologists don’t really know where this group should sit within the diapsid family tree. The reason for this is simple — a complete lack of protopterosaurs that might link this group to other diapsids.” — David Unwin in The Pterosaurs from Deep Time.

Unfortunately, such statements give ammunition to Creationists, because it sounds like pterosaurs were “specially created” and nothing could be further from the truth. So this damages the good names of both Paleontology and Science and can only be repaired by professional paleontologists with PhDs. I’ve done and continue doing my part.

To put the final nail in the coffin
No paleontologist has been able to put forth even a short series of taxa that demonstrate a gradual accumulation of pterosaurian traits within the Archosauria or Archosauriformes.

We also talked about this and solved this problem in the first four PterosaurHeresies.com blogs here, here, here and here.

It’s actually THIS EASY to solve the problem:
If you include several hundred representatives from the gamut of prehistoric reptiles in phylogenetic analysis, at least by default and at best by shared homologies, you will recover some taxa that will nest closer to pterosaurs than to other reptiles. So it’s the shame of paleontology that no one else has attempted this time-consuming, but otherwise relatively easy task by expanding the taxon list to include lepidosauromorphs, lizards, tritosaurs and fenestrasaurs. Actually it can be done with as few as a dozen key taxa if you’re pressed for time, as already shown in an academic publication (Peters 2000). The taxa it promotes continue to be ignored by all other workers* in one of the more interesting feuds/wars in the history of paleontology. I don’t care if you ignore the paper. Don’t ignore the taxa.

*Except Senter 2003, who bungled his observations and provided cartoons for figures. To be fair, I also made freshman mistakes tracing the same difficult taxa, but corrected them here, here and here.

History of the Ornithodira
In the earliest days of phylogenetic analysis, Gauthier & Padian (1985) placed pterosaurs within the clade Ornithosuchidae (Huene 1914) along with Lagosuchus (= Marasuchus (Sereno & Arcucci 1994)), and the Dinosauria.

Figure 2. A tree recovered from Gauthier 1986 (form Wiki) Pararchosauriformes are in green boxes. Pterosaurs are included within Ornithodira. Pink arrows point to crocs and dinos (which, sans pteros, make up the Archosauria in the large reptile tree.)

Later, Gauthier (1986, Fig. 2) noted that the position of pterosaurs and Marasuchus with respect to dinosaurs was not resolved, but found the three formed a monophyletic group he called the Ornithodira. Sereno (1991) followed and expanded on this by including Scleromochlus.

While reviewing Sereno (1991), Kellner (1996) concluded that no particular character linked pterosaurs to the Archosauria (sensu stricto), but added that because of several shared derived characters with basal dinosauromorphs, the traditional hypothesis was the best supported at the time.

Peters (2000) added several taxa (Langobardisaurus, Cosesaurus, Sharovipteryxand Longisquama) that had been excluded in prior studies to three prior phylogenetic analyses and recovered trees in which these taxa nested closer to pterosaurs than any included archosaur. Refinements to the observed morphologies and expansion in the taxon list (both chronicled in PterosaurHeresies.com and ReptileEvolution.com) have further cemented these relationships.

Ornithodira Defined
Gauthier (1986) defined “Ornithodira” as all forms closer to birds than to crocodiles. Here, based on the topology recovered by the large reptile tree (with an unmatched gamut) this definition is redundant with an earlier one (Gauthier and Padian 1985) made for Ornithosuchia.

Sereno (1991) re-defined “Ornithodira” as the last common ancestor of the dinosaurs and the pterosaurs, and all its descendants.

Ornithodira TrashedHere, based on a larger tree that separates the pterosaurs from the dinosaurs on separate branches that divided in the earliest Carboniferous, the definition of Ornithodira is redundant with Reptilia. This can be easily tested with far fewer taxa. Not sure why paleontologists have not done so. Tradition is cozy and comfortable, but no discoveries have ever been made in comfort.

As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

4 thoughts on “Ornithodira: Avoid this taxon!”

Sadly, for all your bluster about how well founded your analysis is, for all the upset it will provide to all of published analyses, you refuse to get it published. If, as you say, your analysis is sound, it would be excellent to provide proofs in the form of phylogenetic analysis and careful, character-by-character descriptive reasoning for states and their viability. You try to do this here on this blog, but don’t try to publish it. I suggest going forward with that plan, so that it, like your previously published (though contradicted) analysis on pterosaur origins may be assessed.

I will also say that you have the right of Ornithodira if your premise of affinities for them are correct, that it would pertain to a much broader content … but that is the way of things with phyogenetic definitions: You define it securely, and leave it be, so whichever content it contains down the road, that is its content — the definition is stable. Warning people to avoid Ornithodira because you don’t like the implied relationship? Not a wise thing, nor a logical one.

I don’t refuse to publish, Jaime. I submitted this a half dozen times several years ago. The most common response was the requirement to personally examine every specimen in the taxon list, then around 260, currently around 330 for the reptiles alone. If all manuscript candidates have to attempt that Herculean task to get published, good luck to anyone ever getting a large gamut reptile tree published and paleontology can remain in the dark ages.

My analysis of pterosaur origins was contradicted by Senter (2003) who bungled so many observations — and Hone and Benton (2007, 2008), widely held to be two of the worst papers ever published. Recently Bennett (2012) showed that various typos in Hone and Benton were the only reasons why they did not completely duplicate my results, along with other problems. Find out more about Hone and Benton 2007, 2008 by using those key words in this blog.

The definition of Ornithodira is indeed stable, but is redundant with the Reptilia, hence the utility is lost. The definition could just as well be Triceratops, Boa their last common ancestor and all of its descendants.

You know, I agree with you that pterosaurs are more likely related to non-archosaurs like Scleromochlus and Longisquama than to dinosaurs, but your hyperbole doesn’t help your case. Pterosaurs don’t have NOTHING in common with dinosaurs, there IS some evidence for avemetatarsalian pterosaurs, and the quotes from Unwin and Hone and Benton do not imply there is no evidence for the latter. Take bats, of which we have no preserved protobats. Yet there is still evidence of their relationships- molecular evidence of laurasiatherian relationships and morphological evidence of archontan relationships. Also, paleontologists HAVE been able to provide a short set of taxa to go from unambiguous archosaurs to pterosaurs – Crurotarsi (e.g. Ornithosuchus) to Dinosauromorpha (e.g. Lagerpeton) to Scleromochlus to pterosaurs. Maybe it’s worse than your set of taxa, but it still exists. Also, it’s NOT easy to solve the problem. You’ve done a terrible job of trying, as I’ve posted on before, but so has everyone else. To get it right will be hard, as we’ll need to look at hundreds of traits and taxa, and formulate the characters well. Gauthier and Padian (1985) placed pterosaurs in Ornithosuchia, not Ornithosuchidae. Ornithodira may be more inclusive than Avemetatarsalia, though I doubt it will be as inclusive as Reptilia, but if you changed your tone more people would listen.

My tone has just recently risen with the dearth of BS that keeps coming out since 2000. Bat ancestors are known (see reptileevolution.com or blogs herein). Terrible job? Presenting evidence is terrible? Pointing out “strange bedfellows” is terrible? Ready and willing to correct errors is terrible?